Dual system boot, modifying windows and Fedora Boot sequence

I installed Windows and fedora on two hard drives so that I would start Linux by setting the boot hard disk as the 2nd hard drive in the BIOS, and when I started Windows, I had to change to the 1th hard drive.

In fact, in the Grub boot list, there are already windows options, just not the default option, which requires me to modify the boot sequence of the system in the Linux system so that when I start with the 2nd hard drive, Windows is also started by default. So, when a family uses a computer, it doesn't have to worry about the startup option, and when I start Linux, I can manually select the startup item.

In my Fedora:/boot/grub2 directory has a grub.cfg file, first SU root permissions, use VI to open edit this file, modify the default startup items and wait time:

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Set default= "3"

Set timeout=30

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Find the above two sentences, modify the startup item, default is numbered from 0, my Windows is in item 4th.

Timeout is the wait time before entering the system, the unit is S.